In recent display devices, a touch input method in which a user directly touches a screen using a finger or an electronic pen to input is widely used. As such a touch input method can be combined with a display screen without a separate input device such as a keyboard or a mouse, it is advantageously used for a portable terminal such as a smart phone, a notebook computer, and a tablet PC.
In addition, the touch input method can provide an intuitive and convenient user interface by directly touching a specific position of the display screen by a user. Especially, a touch input method using a pen is more accurate than a touch input method using a finger, which is also suitable for performing graphic work such as CAD.
A device used in such a touch input method for converting the coordinates of a pen into digital data is called a digitizer. Depending on the method of detecting coordinates, there are a resistive type, a capacitive type, and an electro-magnetic resonance (EMR) type digitizers.
In an EMR type digitizer, as shown in Korean Patent Laid-Open Publication No. 2015-0103612, a loop coil is disposed on a printed circuit board, and a voltage is applied to the loop coil to control an electromagnetic wave to be generated due to power transmitted so that the generated electromagnetic wave can be absorbed by the EMR pen. Here, the EMR pen may include a capacitor and a loop, and the absorbed electromagnetic wave may be again emitted at a predetermined frequency.
The electromagnetic wave emitted by the EMR pen can be reabsorbed by the loop coil on the printed circuit board again, so that it can be determined which position of the touch screen is close to the EMR pen.
Meanwhile. Korean Patent Laid-Open Publication No. 2015-0103612 discloses that an electrode is formed to have a thickness of 9 to 50 μm, and it is disclosed that when the thickness of the electrode is less than about 9 μm, electrical characteristics may be deteriorated.